Cu-Ni-Si-Co-Cr System Alloy for Electronic Materials

ABSTRACT

The problem to be solved by the present invention is to provide a significant improvement in the properties in Cu—Ni—Co—Si alloy by adding Cr, i.e., to provide Corson alloys having high strength and high electrical conductivity. There is provided a copper alloy for electronic materials comprising 1.0 to 4.5 mass % of Ni, 0.50 to 1.2 mass % of Si, 0.1 to 2.5 mass % of Co, 0.003 to 0.3 mass % of Cr, with the balance being Cu and unavoidable impurities, the mass concentration ratio of the total mass of Ni and Co to Si ([Ni+Co]/Si ratio) satisfies the formula: 4≦[Ni+Co]/Si≦5, and with regard to Cr—Si compound whose size is 0.1 to 5 μm dispersed in the material, atomic concentration ratio of Cr to Si in the dispersed particle is 1-5, and area dispersion density thereof is more than 1×10 4 /mm 2 , and not more than 1×10 6 /mm 2 .

TECHNICAL FIELD

The present invention relates to precipitation hardening copper alloys, in particular, to Cu—Ni—Si—Co—Cr system alloys suitable for use in a variety of electronic components.

BACKGROUND ART

A copper alloy for electronic materials that are used in a lead frame, connector, pin, terminal, relay, switch, and various other electronic components is required to satisfy both high strength and high electrical conductivity (or thermal conductivity) as basic characteristics. In recent years, as high integration and reduction in size and thickness of an electronic component have been rapidly advancing, requirements for copper alloys used in these electronic components have been increasingly becoming severe.

Recently, because of considerations related to high strength and high electrical conductivity, the amount in which precipitation-hardened copper alloys are used has been increasing, replacing conventional solid-solution strengthened copper alloys typified by phosphor bronze and brass as copper alloys for electronic components. With a precipitation-hardened copper alloy, the aging of a solution-treated supersaturated solid solution causes fine precipitates to be uniformly dispersed and the strength of the alloys to increase. At the same time, the amount of solved elements in the copper is reduced and electrical conductivity is improved. For this reason, it is possible to obtain materials having excellent strength, spring property, and other mechanical characteristics, as well as high electrical and thermal conductivity.

Among precipitation hardening copper alloys, Cu—Ni—Si copper alloys commonly referred to as Corson alloys are typical copper alloys having relatively high electrical conductivity, strength, stress relaxation property, and bending workability, and are among the alloys that are currently being actively developed in the industry. In these copper alloys, fine particles of Ni—Si intermetallic compounds are precipitated in the copper matrix, thereby increasing strength and electrical conductivity.

It is known that characteristics of Cu—Ni—Si copper alloys are improved by adding Co and Cr. Co and Cr are similar to Ni in forming a compound with Si and increasing mechanical strength.

Japanese Patent Application Publication No. 2006-283120 (Patent Document 1) discloses that a dramatic improvement in the properties (especially, the strength and electrical conductivity) of a Co and Cr-containing Cu—Ni—Si alloy is achieved when the size, composition and distribution of inclusion are controlled under certain compositional and manufacturing condition. Specifically, a Cu—Ni—Si—Co—Cr copper alloy for electronic components is described in which the composition is 0.5 to 2.5 mass % of Ni, 0.5 to 2.5 mass % of Co, and 0.30 to 1.2 mass % of Si, 0.09 to 0.5 mass % of Cr with the balance being Cu and unavoidable impurities, the mass concentration ratio of the total mass of Ni and Co to the mass of Si ([NH+Co]/Si ratio) in the alloy composition satisfies the formula: 4≦[Ni+Co]/Si≦5, the mass concentration ratio of Ni and Co (Ni/Co ratio) in the alloy composition satisfies the formula 0.5≦Ni/Co≦2, and with regard to the number of inclusion (P) whose size is 1 μm or more dispersed in the material and the number of said inclusion containing 10 mass % or more of carbon (Pc), Pc is 15 per 1000 μm² or less and the ratio (Pc/P) is 0.3 or less.

Japanese Patent Application Publication No. 2005-113180 (Patent Document 2) aims at the compound of Cr and Si which precipitates in a copper alloy while it is not a Cu—Ni—Si copper alloy. The Document says that when CrSi compound having a given size and area number density is finely precipitated in Cu matrix and the size of Cr compound other than CrSi is restricted, etchability may be ensured while the punching quality is improved. Further, a copper alloy having good etchability and punching quality for electric components is described in which the composition is 0.1 to 0.25 weight % of Cr, 0.005 to 0.1 weight % of Si, 0.1 to 0.5 weight % of Zn, and 0.05 to 0.5 weight % of Sn, with the balance being Cu and unavoidable impurities, the weight ratio of Cr and Si is 3-25, CrSi compounds whose size is 0.05 μm to 10 μm are present in a copper matrix at area number density of 1×10³ to 5×10⁵/mm², and the size of Cr compounds (other than CrSi compound) is 10 μm or less. The Document discloses that for preparing said copper alloy, it is necessary that the temperature for heating treatment before hot working is 850 to 980° C., and after said working, a process comprising a cold working and a heat treatment at 400 to 600° C. is performed one or more times.

[Patent Document 1] Japanese Patent Application Publication No. 2006-283120

[Patent Document 2] Japanese Patent Application Publication No. 2005-113180

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

In recent years, as high integration and reduction in size and thickness of an electronic component have been rapidly advancing, a dramatic improvement in properties of Cu—Ni—Si—Co—Cr system alloy which is the alloy system according to the present invention, is also required.

However, Patent Document 1 does not describe Cr—Si compounds.

Patent Document 2 describes that controlling the area number density and size of Cr—Si compounds improves the working properties for etching and press-punching. However, in this Document, Ni is not added, and therefore, it is merely required to consider the conditions for preparing Cr—Si without considering formation of Ni—Si compounds and Co—Si compounds. Therefore, in this Document, it is not discussed how Cr—Si compounds should be controlled in Cu—Ni—Si—Co—Cr system alloy.

Accordingly, the problem to be solved by the present invention is to improve the properties of Cu—Ni—Si—Co—Cr system alloy by controlling the state of precipitation of Cr—Si compounds in said alloy.

Means for Solving the Problem

The present inventors conducted thoroughgoing research in order to solve the above-described problems, and have found the following inventions. The present invention provides Cu—Ni—Si—Co—Cr system alloy in which Si is in excess of Ni and Co to ensure the precipitation of Ni silicide in the corresponding amount of added Ni and Co silicide in the corresponding amount of added Co for increasing the strength, while the excessive Si forms compound with added Cr for obtaining high electric conductivity. The important point of the present invention is to control the growth of the compound from Cr and Si, in order to prevent the shortage of Si, which is to be combined with Ni and Co, by overgrowth of Cr—Si compound. Specifically, the present inventors turned our attention to the composition and size of the Cr—Si compound and area number density thereof, and thus, found that the effect can be increased by controlling the temperature during the heat treatment and rate of cooling.

Namely, the present inventions are as follows:

(1) A copper alloy for electronic materials in which the composition is 1.0 to 4.5 mass % of Ni, 0.50 to 1.2 mass % of Si, 0.1 to 2.5 mass % of Co, 0.003 to 0.3 mass % of Cr, with the balance being Cu and unavoidable impurities, the mass concentration ratio of the total mass of Ni and Co to Si ([Ni+Co]/Si ratio) satisfies the formula: 4≦[Ni+Co]/Si≦5, and with regard to Cr—Si compound whose size is 0.1 to 5 μm dispersed in the material, atomic concentration ratio of Cr to Si in the dispersed particle is 1-5, and area dispersion density thereof is more than 1×10⁴/mm², and not more than 1×10⁶/mm² (2) The copper alloy for electronic materials described in (1) wherein area dispersion density of the Cr—Si compound whose size is more than 5 μm dispersed in the material is not more than 50/mm² (3) The copper alloy for electronic materials described in (1) or (2) wherein the alloy further comprises one or more selected from Sn and Zn at 0.05-2.0 mass % (4) The copper alloy for electronic materials described in any of (1)-(3) wherein the alloy further comprises one or more selected from Mg, Mn, Ag, P, As, Sb, Be, B, Ti, Zr, Al and Fe at 0.001-2.0 mass % (5) A wrought copper alloy product made of the copper alloy described any of (1)-(4). (6) Electronic components comprising the copper alloy described any of (1)-(5).

EFFECT OF THE INVENTION

In accordance with the present invention, a Cu—Ni—Si—Co—Cr system alloy for electronic materials having improved strength and electrical conductivity can be obtained because the effect of addition of Cr which is an element for alloy is more effectively exerted.

PREFERRED EMBODIMENTS OF THE INVENTION (1) Addition Amount of Ni, Co and Si

Ni, Co and Si form an intermetallic compound with appropriate heat-treatment and make it possible to increase strength without adversely affecting electrical conductivity. Addition amount of Ni, Co and Si will be examined below, respectively.

As for Ni and Co, it is necessary for the copper alloy for electronic materials to include 1.0 to 4.5 mass % of Ni and 0.1-2.5 mass % of Co so that the alloy may satisfy an appropriate strength and electrical conductivity. Preferably, the alloy should include 1.0 to 2.0 mass % of Ni and 1.0 to 2.0 mass % of Co, and more preferably, 1.2 to 1.8 mass % of Ni and 1.2 to 1.8 mass % of Co. However, when the addition amounts of Ni and Co are such that Ni is less than 1.0 mass % and Co is less than 0.1 mass %, respectively, the desired strength cannot be achieved, and conversely, the addition amounts are such that Ni is greater than 4.5 mass % and Co is greater than 2.5 mass %, respectively, higher strength can be achieved, but electrical conductivity is dramatically reduced and hot workability is furthermore impaired.

As for Si, it is necessary for the copper alloy for electronic materials to include 0.30 to 1.2 mass % of Si so that the alloy may satisfy an objective strength and electrical conductivity. Preferably, the alloy should include 0.5 to 0.8 mass % of Si. However, when the addition of Si is such that Si is less than 0.3 mass %, the desired strength cannot be achieved, and conversely, when the addition amount is such that Si is greater than 1.2 mass %, higher strength can be achieved, but electrical conductivity is dramatically reduced and hot workability is furthermore impaired.

In the present invention, the weight concentration ratio of the total amount of Ni and Co to Si ([Ni+Co]/Si) in the alloy composition is further defined.

In the present invention, Ni/Si ratio is set at lower side of specified range 3≦Ni/Si≦7 previously reported, namely, Si is added slightly more than usual, and thereby, Ni and Co are converted into Ni silicide and Co silicide thoroughly, and thus, reduction of electrical conductivity caused by solid solution of excess Ni and Co which do not contribute the precipitation may be reduced. However, in the case where the weight concentration rate satisfies [Ni+Co]/Si<4, the electrical conductivity reduces by solved Si due to too high rate of Si, and further, solderability deteriorates due to formation of oxide layer of SiO₂ on the surface of the material during annealing process. The alloy tends to form coarse Ni—Co—Si particles which do not contribute to strengthening, and in fact said particles have a tendency to give a starting point from which cracks are generated during a bending process and parts where a metal plating cannot be well deposited. On the other hand, in the case where the rate of Ni and Co to Si is increased, and [Ni+Co]/Si>5 is satisfied, the electrical conductivity is dramatically reduced, and therefore, it is not desirable for an electronic material.

Therefore, in the present invention, [Ni+Co]/Si ratio in the alloy composition is controlled so that 4≦[Ni+Co]/Si≦5 is satisfied.

The [Ni+Co]/Si ratio preferably satisfies 4.2≦[Ni+Co]/Si≦4.7.

It is believed that both of Ni and Co not only contribute to generation of compound but also associate mutually, so that they improve the properties of the alloy. It is also possible to further improve the properties by controlling the weight concentration ratio of Ni and Co (Ni/Co ratio) in the alloy composition. Preferably, the Ni/Co ratio should be set within the range 0.5≦N/Co≦2 in which a remarkable improvement of strength can be observed. The range 0.8≦N/Co≦1.3 is more preferable.

Addition Amount of Cr

In the Cu—Ni—Si—Co alloy, when the concentrations of Ni, Si and Co are increased, the total number of precipitated particles increases, and therefore, higher strength can be achieved by precipitation strengthening. On the other hand, with the increases of concentration by addition, the amount of solid solution which does not contribute to the precipitation also increases, and therefore the electrical conductivity reduces and though peak strength of age-precipitation is increased, the electrical conductivity finally reduces at the peak strength. However, when 0.003-0.3 mass % of Cr, preferably 0.01-0.1 mass % of Cr is added into said Cu—Ni—Si—Co alloy, the electrical conductivity can be finally increased without sacrificing strength as compared with Cu—Ni—Si—Co alloy containing Ni, Si and Co at the same concentration and further, hot workability is improved, and thus yield becomes high.

While the particle which is precipitated when Cr is added into Cu—Ni—Si—Co alloy tends to be precipitated as particles of simple substance having bcc structure primarily composed of Cr, compounds with Si also tend to be precipitated. As for Cr, chromium silicide (Cr₃Si and the like), which is a compound of Cr with Si, can be easily precipitated in the copper matrix by an appropriate heat treatment. Therefore, solid solved Si component which has not been precipitated as Ni₂Si, CoSi₂ and the like can be precipitated as Cr—Si compound during the process in which the properties of alloy are tailored using combination of solution treatment, cold rolling, and aging treatment. Therefore, reduction of the electrical conductivity by solid solved Si can be suppressed, and it is possible to increase the electrical conductivity without adversely affecting strength.

In this process, when Si concentration in Cr particle is low, Si remains in the matrix, and therefore the electrical conductivity reduces. On the other hand, when the concentration of Si in the Cr particle is high, Si concentration is reduced which is required for precipitating Ni—Si particle and Co—Si particle, and therefore strength is reduced. Further, when Si concentration in Cr is high, coarse Cr—Si compounds increase and thus bending workability, fatigue strength and the like are deteriorated. Further, when the rate of cooling after solution treatment is slow or aging heat treatment is excessively prolonged, coarse Cr—Si compound is produced and thus the concentration of Si required for forming Ni—Si compound reduces. Therefore, Ni—Si compound which contributes to strengthening becomes insufficient. This occurs due to the fact that diffusion rates of Si and Cr in Cu are faster than that of Ni or Co, and thus Cr—Si compound tends to become a coarse one, and therefore precipitation rate of Cr—Si compound is faster than that of Ni—Si compound or Co—Si particle.

Accordingly, when the cooling rate after solution treatment is controlled and the condition that the temperature and time are higher and longer than the aging condition which gives the maximum strength is avoided, the composition, size and density of Cr—Si compound can be controlled. Therefore, Cr concentration is set at 0.003 mass % or more, and 0.3 mass % or less, and the atomic concentration ratio of Cr to Si is set at 1-5.

Further, Cr preferentially precipitates along crystal grain boundaries in the cooling process at the time of casting. Therefore the grain boundaries can be strengthened, cracking during hot working is less liable to occur, and a reduction in yield can be suppressed. In other words, Cr that has precipitated along the grain boundaries during casting is solved by solution treatment or the like, but forms suicide in the subsequent aging precipitation. With an ordinary Cu—Ni—Si alloy, the portion of the added Si solved in the matrix, which has not contributed to aging precipitation, suppresses an increase in electrical conductivity. However, by adding Cr as a silicide-forming element that causes silicide to further precipitate, the Si content solved in the matrix can be reduced as compared with the conventional Cu—Ni—Si—Co alloy and electrical conductivity can be increased without compromising strength.

Size and Dispersion Density of Cr—Si Compounds

Size of Cr—Si compounds affects bending workability, fatigue strength and the like. In the case where dispersion density of Cr—Si compounds larger than 5 μm is more than 50/mm² or in the case where dispersion density of Cr—Si compounds the size of which is 0.1-5 μm is more than 1×10⁶/mm², bending workability, and fatigue strength remarkably deteriorate. Further, area number density affects excess and deficiency of Si concentration in the matrix, and therefore, desired strength characteristics cannot be obtained in the state where many large particles are dispersed. Therefore, it is preferable to make the dispersion density of Cr—Si compounds having the size of over 5 μm not more than 50/mm², preferably, not more than 30/mm², and more preferably, not more than 10/mm². As for Cr—Si compounds having the size of 0.1-5 μm, dispersion density should be not more than 1×10⁶/mm², preferably, not more than 5×10⁶/mm², more preferably, not more than 1×10⁶/mm². Further, when the dispersion density is 1×10⁴/mm² or less, the improvement effect by Cr addition is small, and therefore it is desired to exceed it. In the typical embodiment, it is 1×10⁶/mm² or more.

Sn and Zn

One or more elements selected from Sn and Zn can be added in a total amount of 0.05-2.0 mass % for improving stress relaxation characteristics and the like without considerably compromising strength and electrical conductivity. The addition amount thereof is preferably 0.05-2.0 mass %, because the effect is insufficient when it is less than 0.05 mass %, and when it exceeds 2.0 mass %, manufacturability such as casting properties, electrical conductivity of the product are compromised.

Other Elements for Addition

The addition of Mg, Mn, Ag, P, As, Sb, Be, B, Ti, Zr, Al and Fe exhibits a variety of effects. These elements complement mutually and improve not only strength and electrical conductivity but also bending workability, plating characteristic, and productivities such as hot workability due to the miniaturization of cast structure. Therefore, one or more elements selected from them can be optionally added in a total amount of not more than 2.0 mass % into the Cu—Ni—Si—Co—Cr system alloy related to the present invention according to the properties required. The addition amount is preferably 0.001-2.0 mass % in total, more preferably, 0.01-1.0 mass %, because when the total amount of these elements is less than 0.001 mass %, the desired effect cannot be obtained, and when it exceeds 2.0 mass %, the electrical conductivity and manufacturability are remarkably reduced.

Further, any element which is not described concretely in the specification of the present application may be added within the range in which no adverse effect occurs.

Next, manufacturing method of the present invention is explained. Cu—Ni—Si—Co—Cr system alloy related to the present invention can be manufactured by the conventional manufacturing method, except the condition of solution-treatment and aging treatment for controlling Ni—Si compound, Co—Si and Cr—Si compound.

Firstly, electrolytic cathode copper, Ni, Si, Co, and other raw materials are melted in an atmospheric melting furnace to obtain molten metal having the desired composition. The molten metal is then cast into an ingot. Hot rolling is carried out thereafter, cold rolling and heat treatment are repeated, and a strip or a foil having a desired thickness and characteristics are finished. The heat treatment includes solution treatment and aging treatment. In the solution treatment, material is heated at a high temperature of about 700 to about 1000° C., the Ni—Si compound, Co—Si compound and Cr—Si compound are solved in the Cu matrix, and the Cu matrix is simultaneously caused to re-crystallize. Hot rolling sometimes serves as the solution treatment.

During the solution treatment, heating temperature and cooling rate are important. Previously, the cooling rate after heating was not controlled. Therefore, water cooling using a tank equipped at the outside of the outlet of a heating furnace, or air cooling with atmosphere was conducted. In this case, cooling rate is variable according to the setting of heating temperature, and therefore, previously, the cooling rate fluctuates in the range of 1° C./sec or less and in the range of 10° C./sec or more. Accordingly, the control of the alloy as shown in embodiments of the present invention was difficult.

It is preferable that the cooling rate is within the range from 1 to 10° C./sec. In an aging treatment, material is heated for 1 hour or more, typically 3 to 24 hours in a temperature range of 350 to 550° C., and Ni—Si compound and Cr—Si compound are precipitated as microparticles. The aging treatment results in increased strength and electrical conductivity. Cold rolling is sometimes performed before and/or after the aging treatment in order to obtain higher strength. Also, stress relief annealing (low-temperature annealing) is sometimes performed after cold rolling in the case where the cold rolling is carried out after aging.

In one embodiment, with Cu—Ni—Si—Co—Cr copper alloy related to the present invention, it is possible that 0.2% yield strength is 750 MPa or more, and electrical conductivity is 50% IACS or more, and further it is also possible that 0.2% yield strength is 800 MPa or more, and electrical conductivity is 50% IACS or more, and further it is also possible that 0.2% yield strength is 850 MPa or more, and electrical conductivity is 50% IACS or more.

The Cu—Ni—Si—Co—Cr system alloy related to the present invention can be used to manufacture various wrought copper alloy products, e.g., plates, strips, tubes, rods, and wires. The Cu—Ni—Si—Co—Cr system alloy according to the present invention can be used in lead frame, connectors, pins, terminals, relays, switches, foil material for secondary batteries, and other electronic components or the like which are required to satisfy both high strength and high electrical conductivity (or thermal conductivity).

EXAMPLES

Examples of the present invention are described below. The examples are provided for facilitating understanding of the present invention and the advantages thereof, and not intended to limit the scope of the invention.

Copper alloys used in Examples of the present invention have the composition in which Sn, Zn, Mg, Mn, Co and Ag are optionally added into the copper alloy in which several contents of Ni, Si, Co and Cr are varied as shown in Table 1. Each of copper alloys used in comparative examples is Cu—Ni—Si—Co—Cr system alloy having a parameter which is out of range of the present invention.

Copper alloys having various compositions shown in Table 1 were melted in a high-frequency melting furnace at 1300° C. and then cast into an ingot having a thickness of 30 mm. Next, the ingot was heated to 1000° C., hot rolled thereafter to a plate thickness of 10 mm, and then rapidly cooled. Next, the metal was faced to a thickness of 8 mm in order to remove scales from the surface, and sheets having a thickness of 0.2 mm were then formed by cold rolling. Solution treatment was subsequently carried out by maintaining the sheets for 120 seconds in Ar gas atmosphere at 800-1000° C. according to the addition amounts of Ni and Cr, and then cooling them to the room temperature at various cooling rates. The cooling rate was controlled by varying gas flow rate blowing against the sample after heating. The cooling rate was determined by measuring the time required for cooling the sample from the highest temperature to 400° C. The cooling rate was 5° C./s when the gas was not blown. In a certain embodiment where the cooling rate was further slower, the cooling rate was 1° C./s when the temperature was reduced with controlling the heating power. The sheets were then cold rolled to 0.1 mm, and lastly subjected to the aging treatment in inert atmosphere at 400-550° C. for 1-12 hours according to the addition amount to manufacture the samples.

Each alloy thus obtained was evaluated for its strength and electrical conductivity. As for strength, 0.2% yield strength (YS: MPa) was measured using a tensile test in the direction paralleling the rolling. Electrical conductivity (EC; % IACS) was obtained by measuring volume resistivity using double bridge.

As for the evaluation of bending workability, 90° bending processing was performed under the condition in which a ratio of the thickness of sample sheet to bending radius is 1 using a W-shaped metal mold. The evaluation was carried out by observing the surface of the bended portion with an optical microscope, and the case where crack was not observed is considered to be “good” since there is practically no problem, and the case where crack was observed is considered to be “bad”. As for fatigue test, alternating stress was loaded according to JIS Z 2273, and stress (MPa) with which repeat number until break is 10⁷ was found.

As for the observation of Cr—Si compound, after electropolishing, by using FE-AES observation (Nihon-Denshi KK, JUMP-7800F), particles whose size is 0.1 μm or more were observed at many positions. Actually, in order to remove the adsorbed elements (C, O) on the surface, sputtering with Ar⁺ was performed, and Auger spectrum of each particle was analyzed. Detected elements were subjected to sensitivity factor method for weight-concentration conversion as semi-quantitative value. The particles in which Cr and Si were detected were chosen for the evaluation below. “Composition (Cr/Si)”, “Size”, and “Area dispersion density” of Cr—Si compound were analyzed by observing Cr—Si particles whose size is 0.1 μm or more at many positions with FE-AES and were respectively evaluated as an average composition, a diameter of the smallest circle, and an average number in each observation field.

The results are shown in Table 1 and 2.

TABLE 1 Solution Cooling Aging Aging Temperature Rate Temperature Time Ni Si Cr Co Sn Zn Others [Ni + Co]/Si (×120 s) (° C./s) (° C.) (h) Example 1 1.8 0.6 0.005 1.0 4.7 800 4 450 6 2 1.8 0.6 0.05 1.0 4.7 800 4 450 6 3 1.8 0.6 0.1 1.0 4.7 800 4 450 6 4 1.8 0.6 0.1 1.0 0.3 0.5 4.7 800 4 450 6 5 1.8 0.6 0.1 1.0 0.3 0.5 0.1Mg 4.7 800 4 450 6 6 1.8 0.6 0.005 1.0 4.7 900 4 450 6 7 1.8 0.6 0.05 1.0 4.7 900 4 450 6 8 1.8 0.6 0.1 1.0 4.7 900 4 450 6 9 1.8 0.6 0.1 1.0 0.3 0.5 4.7 900 4 450 6 10 1.8 0.6 0.1 1.0 0.3 0.5 0.1Mg 4.7 900 4 450 6 11 1.8 0.6 0.005 1.0 4.7 800 10 450 6 12 1.8 0.6 0.05 1.0 4.7 800 10 450 6 13 1.8 0.6 0.1 1.0 4.7 800 10 450 6 14 1.8 0.6 0.1 1.0 0.3 0.5 4.7 800 10 450 6 15 1.8 0.6 0.1 1.0 0.3 0.5 0.1Mg 4.7 800 10 450 6 16 1.8 0.6 0.005 1.0 4.7 900 10 450 6 17 1.8 0.6 0.05 1.0 4.7 900 10 450 6 18 1.8 0.6 0.1 1.0 4.7 900 10 450 6 19 1.8 0.6 0.1 1.0 0.3 0.5 4.7 900 10 450 6 20 1.8 0.6 0.1 1.0 0.3 0.5 0.1Mg 4.7 900 10 450 6 21 4 1.2 0.2 2.0 5.0 1000 10 450 6 22 1.2 0.6 0.3 1.5 4.5 950 10 450 6 23 2.5 1 0.1 1.5 4.0 950 10 450 6 24 4 1 0.1 0.2 4.2 950 10 450 6 Area dispersion Area dispersion Density of Density of Cr—Si particles Cr—Si particles of greater than Composition 0.1-5 micrometers 5 micrometers of Bending (×10⁶/mm²) (/mm²) Cr—Si particle YS EC Workability Fatigue Example 1 0.26 8 3.1 740 53 Good 270 2 0.40 12 3.1 745 54 Good 280 3 0.87 26 2.9 745 55 Good 275 4 0.87 26 2.9 770 53 Good 280 5 0.87 26 2.9 790 52 Good 280 6 0.22 7 3.0 790 50 Good 285 7 0.34 10 3.0 795 51 Good 290 8 0.75 22 2.8 795 52 Good 295 9 0.75 22 2.8 820 50 Good 300 10 0.75 22 2.8 840 49 Good 305 11 0.20 6 2.7 780 51 Good 270 12 0.32 10 2.7 785 52 Good 280 13 0.70 21 2.5 785 53 Good 280 14 0.70 21 2.5 810 51 Good 280 15 0.70 21 2.5 830 50 Good 305 16 0.18 5 2.6 820 48 Good 300 17 0.28 8 2.6 825 49 Good 305 18 0.60 22 2.4 825 50 Good 305 19 0.60 18 2.4 850 48 Good 310 20 0.60 18 2.4 870 47 Good 315 21 0.96 31 2.8 963 43 Good 330 22 0.87 28 3.2 805 53 Good 290 23 0.91 30 2.4 855 50 Good 310 24 0.67 22 2.4 863 44 Good 310

TABLE 2 Solution Cooling Aging Aging Temperature Rate Temperature Time Ni Si Cr Co Sn Zn Others [Ni + Co]/Si (× 120 s) (° C./s) (° C.) (h) Comparative 1 1.8 0.6 0.005 3.0 800 4 450 6 Examples 2 1.8 0.6 0.05 3.0 800 4 450 6 3 1.8 0.6 0.1 3.0 800 4 450 6 4 1.8 0.6 0.1 0.3 0.5 3.0 800 4 450 6 5 1.8 0.6 0.1 0.3 0.5 0.1Mg 3.0 800 4 450 6 6 1.8 0.6 0.005 3.0 800 10 450 6 7 1.8 0.6 0.05 3.0 800 10 450 6 8 1.8 0.6 0.1 3.0 800 10 450 6 9 1.8 0.6 0.1 0.3 0.5 3.0 800 10 450 6 10 1.8 0.6 0.1 0.3 0.5 0.1Mg 3.0 800 10 450 6 11 1.8 0.6 — 3.0 800 4 450 6 12 1.8 0.6 — 1.0 4.7 900 4 450 6 13 1.8 0.6 0.05 1.0 4.7 900 0.5 450 6 14 1.8 0.6 0.1 1.0 4.7 900 0.5 450 6 15 1.8 0.6 0.05 1.0 4.7 900 15 450 6 16 1.8 0.6 0.1 1.0 4.7 900 15 450 6 17 1.8 0.6 0.1 1.0 4.7 900 10 600 6 18 1.8 0.6 0.1 1.0 4.7 900 10 600 6 19 1.8 0.6 0.5 1.0 4.7 900 10 450 6 20 1.8 0.6 0.5 1.0 4.7 900 4 450 6 Area dispersion Area dispersion Density of Density of Cr—Si particles Cr—Si particles of greater than Composition 0.1-5 micrometers 5 micrometers of Bending (× 10⁶/mm²) (/mm²) Cr—Si particle YS EC Workability Fatigue Comparative 1 0.10 3 3.3 730 47 Good 265 Examples 2 0.13 4 3.3 735 48 Good 270 3 0.17 5 3.1 735 49 Good 270 4 0.17 5 3.1 750 47 Good 275 5 0.17 5 3.1 770 46 Good 280 6 0.08 2 2.8 760 44 Good 270 7 0.10 3 2.8 765 45 Good 265 8 0.14 4 2.7 765 46 Good 265 9 0.14 4 2.7 780 44 Good 270 10 0.14 4 2.7 800 43 Good 275 11 — — — 730 43 Good 290 12 — — — 785 45 Good 290 13 13 55 3.0 705 55 Bad 205 14 17 72 2.8 715 54 Bad 210 15 0.03 0 23.0 770 46 Good 275 16 0.09 0 26.0 780 45 Good 280 17 16 66 6.0 685 57 Bad 245 18 20 87 7.0 695 56 Bad 250 19 11 47 3.1 765 46 Bad 275 20 15 64 3.1 735 52 Bad 260

In Examples 1-24 of the present invention, as a suitable range of cooling rate was employed, and therefore area dispersion density of Cr—Si compound is 1×10⁶ or less, and Cr/Si is 1-5, and therefore, excellent properties were obtained.

On the other hand, Co was not included in Comparative Examples 1-10, and Cr was not included in Comparative Examples 11 and 12, and therefore, the strength and electrical conductivity could not be achieved at high level. In Comparative Examples 13 and 14, sufficient strength was not obtained because Cr—Si was overgrown due to too slow coding rate, and further, bending workability was also poor.

In Comparative Examples 15 and 16, strength and electrical conductivity were deteriorated because excessive Si remained in the alloy since Cr—Si compound did not grow due to fast cooling rate. In Comparative Examples 17 and 18, sufficient strength could not be obtained because Cr—Si compound was overgrown since aging temperature was high, and bending workability was also poor. Further, Cu, Ni and the like diffused into the coarse particles, and thus Si concentration decreased in the particles, and therefore Cr/Si rate relatively increased. In Comparative Examples 19 and 20, as Cr concentration was too high, Cr—Si compound was overgrown, and therefore sufficient strength could not be obtained and bending workability was also poor. 

1. A copper alloy for electronic materials comprising 1.0 to 4.5 mass % of Ni, 0.50 to 1.2 mass % of Si, 0.1 to 2.5 mass % of Co, 0.003 to 0.3 mass % of Cr, with the balance being Cu and unavoidable impurities, the mass concentration ratio of the total mass of Ni and Co to Si ([Ni+Co]/Si ratio) satisfies the formula: 4≦[Ni+Co]/Si≦5, and with regard to Cr—Si compound particles whose size is 0.1 to 5 μm dispersed in the material, the atomic concentration ratio of Cr to Si in the dispersed particle is 1-5, and area dispersion density thereof is more than 1×10⁴/mm², and not more than 1×10⁶/mm².
 2. The copper alloy for electronic materials according to claim 1 wherein area dispersion density of the Cr—Si compound particles whose size is more than 5 μm dispersed in the material is not more than 50/mm².
 3. The copper alloy for electronic materials according to claim 1 wherein the alloy further comprises one or more of Sn and Zn at 0.05-2.0 mass %.
 4. The copper alloy for electronic materials according to claim 1 wherein the alloy further comprises one or more of Mg, Mn, Ag, P, As, Sb, Be, B, Ti, Zr, Al and Fe at 0.001-2.0 mass %.
 5. A wrought copper alloy product made of the copper alloy according to any one of claims 1-4.
 6. Electronic components comprising the copper alloy according to any one of claims 1-4.
 7. Electronic components comprising a wrought copper alloy product according to claim
 5. 